E-mail window won't expand

Until a couple of day ago, there was an arrow at the right of the screen to close the ad and have the message expand to the right and fill the box.  Now, the arrow is gone and the ad is gone, but the message remains shrunk and there's blank space to the right of the message.  That space can't be expanded.

What, oh what has Cox done this time?  Any idea?

Thanks,